reporter: this morning the secretary of homeland security janet napolitano this is traveling in monrewl canada has been speaking to a group and advocating very strongly that 190 countries take the next store up in airport screening by advocating the use of these full body scanners. in an interview with usa today she said we need to move to the next stage of screenings. there continues to be a threat stream about taking down a commercial airliner in part because it was used successfully before and could have a huge impact. just to give you context here. if there is a piece of advice i've had over the years it's like terrorism is like water it takes the path of least resistance and we are dealing with a thinking enemy. they understand the type of improvements we've made for the screening process, that's why we saw the evolution in the type of attack with the attempted bombing on christmas day, with the underwear -- with the bomb concealed in the underwear. that is an evolution in the tactic and it's also an indicator that when it comes to airline security al-qaida and others are watching what we